Clamshell presses are frequently used to die cut cardboard, plastic sheets, corrugated board and the like. They are well known in the art as shown, for example, in U.S. Pat. No. 5,997,453, the entire content of which is hereby incorporated herein by reference.
Currently, clamshell presses have not been extensively used to die cut structural board such as Falcon Board or Xaniata Board. The manufacturers of these boards advise their customers to convert (cut to shape) the boards using router/plotter tables. It has not been believed that such boards could be die cut or die cut with the same edge quality as a router table. This is because the boards collapse while die cutting or the edge quality is poor and not acceptable to the user.
It has been found that these structural boards can be successfully die cut using special two inch and even three inch tooling. However, this requires a press with an opening of three inches. Since standard tooling height worldwide is 0.937 inches (with some 1.125 inch configurations) this would require significant changes to the press.
It is known to construct clamshell presses with three inch openings to accommodate three inch knives. When a run using smaller knives is to be done, either extensive timely adjustments have to be made to the press or filler plates can be used. While the use of filler plates may achieve the desired press opening or shut height, it is still time consuming and dangerous to employ them as they are very heavy and bulky. It frequently takes several men and heavy equipment to move a filler plate.
Furthermore, while the use filler plates may be possible with smaller presses, they would be totally impractical with the size of presses that are needed to convert structural board. The market for structural boards is large format, i.e., 63″×108″ and 63″×123″. Thus, while it is theoretically possible to design a press for a three inch opening to accommodate a three inch knife and incorporate removable filler plates, it simply is not viable to utilize such large filler plates. Filler plates of this size would weigh thousands of pounds.
There is, therefore, a need for a clamshell die cutting press that is large enough to effectively convert structural board but wherein the press opening can be easily and quickly reduced without requiring the use of filler plates.